U.S. patent application number 14/900821 was filed with the patent office on 2016-05-19 for formulations for producing indium oxide-containing layers, process for producing them and their use.
The applicant listed for this patent is EVONIK DEGUSSA GMBH, Alexey MERKULOV, Jurgen STEIGER. Invention is credited to Arne HOPPE, Alexey MERKULOV, Juergen STEIGER.
Application Number | 20160141177 14/900821 |
Document ID | / |
Family ID | 50639488 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160141177 |
Kind Code |
A1 |
STEIGER; Juergen ; et
al. |
May 19, 2016 |
FORMULATIONS FOR PRODUCING INDIUM OXIDE-CONTAINING LAYERS, PROCESS
FOR PRODUCING THEM AND THEIR USE
Abstract
The present invention relates to liquid formulations which can
be produced by dissolving at least one indium alkoxide compound
which can be prepared by reacting an indium trihalide InX.sub.3
where X=F, Cl, Br, I with a secondary amine of the formula
R'.sub.2NH where R'=alkyl in a molar ratio of from 8:1 to 20:1 to
the indium trihalide in the presence of an alcohol of the generic
formula ROH where R=alkyl in at least one solvent, a process for
producing them, their use for producing indium oxide-containing or
(semi)conducting layers and processes for producing indium
oxide-containing layers which use the formulation of the
invention.
Inventors: |
STEIGER; Juergen; (Taipei
City, TW) ; MERKULOV; Alexey; (Recklinghausen,
DE) ; HOPPE; Arne; (Herne, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
STEIGER; Jurgen
MERKULOV; Alexey
EVONIK DEGUSSA GMBH |
Taipei City
Recklinghausen
Essen |
|
CN
DE
DE |
|
|
Family ID: |
50639488 |
Appl. No.: |
14/900821 |
Filed: |
April 28, 2014 |
PCT Filed: |
April 28, 2014 |
PCT NO: |
PCT/EP2014/058615 |
371 Date: |
December 22, 2015 |
Current U.S.
Class: |
438/478 ;
106/285; 106/287.18; 427/58; 438/660 |
Current CPC
Class: |
H01L 21/288 20130101;
C23C 18/143 20190501; H01L 21/02628 20130101; H01L 21/02664
20130101; C07F 5/00 20130101; H01L 21/02565 20130101; H01L 21/02488
20130101; C23C 16/46 20130101; C23C 18/1216 20130101; C23C 16/407
20130101; H01L 21/02623 20130101; H01L 21/02381 20130101; C23C
16/48 20130101 |
International
Class: |
H01L 21/288 20060101
H01L021/288; C23C 16/46 20060101 C23C016/46; H01L 21/02 20060101
H01L021/02; C23C 16/48 20060101 C23C016/48 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 25, 2013 |
DE |
10 2013 212 019.2 |
Claims
1. A liquid formulation produced by dissolving at least one indium
alkoxide compound in at least one solvent, the at least indium
aloxide compound being prepared by a process comprising: reacting
an indium trihalide InX.sub.3 where X=F, Cl, Br, I with a secondary
amine of the formula R'.sub.2NH where R'=alkyl, at a molar ratio of
from 8:1 to 20:1 to the indium trihalide; and in the presence of an
alcohol of the formula ROH where R=alkyl.
2. The liquid formulation according to claim 1, wherein the indium
alkoxide compound has the formula
[In.sub.6(O)(OR).sub.12X.sub.6].sup.2-A.sub.m.sup.z (ROH).sub.x;
where R=alkyl, X=F, Cl, Br, I, A=cation, z=valency of the cation,
mz=2 and x=0 to 10.
3. The liquid formulation according to claim 2, wherein the indium
alkoxide compound has the formula
[In.sub.6(O)(OMe_).sub.12Cl.sub.6].sup.2--[NH.sub.2R.sub.2].sup.+.sub.2
(MeOH).sub.2.
4. The liquid formulation according to claim 1, comprising the
indium alkoxide compound in a proportion of from 0.1% to 10% by
weight based on the total mass of the liquid formulation.
5. The liquid formulation according to claim 1, wherein the at
least one solvent is selected from the group consisting of a
primary alcohol, a secondary alcohol, a tertiary alcohol, an
aromatic alcohol, an ether, an ester, an aromatic hydrocarbon and a
nitrile.
6. The liquid formulation according to claim 1, wherein the at
least one solvent is selected from the group consisting of
methanol, ethanol, butanol, tetrahydrofurfuryl alcohol, phenol,
2-methoxyethanol, 1-methoxy-2-propanol, tetrahydrofuran, anisole,
butyl acetate, 1-methoxy-2-propyl acetate (PGMEA), ethyl benzoate,
ethylene glycol diacetate, ethyl lactate, butyl lactate, toluene,
xylene and acetonitrile.
7. The liquid formulation according to claim 6, comprising at least
three solvents; wherein: one of the at least three solvents is
selected from the group consisting of ethyl lactate, anisole,
tetrahydrofurfuryl alcohol, butyl acetate, ethylene glycol
diacetate and ethyl benzoate; and the other two of the at least
three solvents have a boiling point difference of at least
30.degree. C. under standard ambient temperature and pressure
conditions.
8. The liquid formulation according to claim 1, comprising three
solvents which are ethanol, 1-methoxy-2-propanol and
tetrahydrofurfuryl alcohol.
9. The liquid formulation according to claim 1, being essentially
water-free.
10. A process for producing the liquid formulation according to
claim 1, comprising: dissolving the at least one indium alkoxide
compound in the at least one solvent.
11. A process for producing an indium oxide-containing layer,
comprising: applying the liquid formulation according to claim 1 to
a substrate.
12. A process for producing a semiconducting layer or a conductive
for an electronic component, comprising: applying the liquid
formulation according to claim 1 to a substrate.
13. A process for producing an indium oxide-containing layer,
comprising: applying the liquid formulation according to claim 1 to
a substrate; and converting the applied liquid formulation by means
of heat and/or electromagnetic radiation.
14. The process according to claim 13, the applied liquid
formulation is converted by means of heat and electromagnetic
radiation.
Description
[0001] The present invention relates to formulations for producing
indium oxide-containing layers, a process for producing them and
their use.
[0002] The production of semiconducting electronic component layers
by means of pressure deposition processes and other liquid
deposition processes makes it possible to achieve far lower
production costs compared to many other processes, e.g. chemical
vapour deposition (CVD), since the deposition of the semiconductor
can in this case be carried out in a continuous process. In
addition, in the case of relatively low process temperatures, there
is the opportunity of also working on flexible substrates and
optionally achieving optical transparency of the printed layers
(especially in the case of very thin layers and in particular in
the case of oxidic semiconductors). Here and in the following, the
term semiconducting layers is used to refer to layers which have a
charge carrier mobility of from 1 to 50 cm.sup.2/Vs in a component
having a channel length of 20 .mu.m at a gate-source voltage of 50
V and a source-drain voltage of 50 V.
[0003] Since the material of the component layer to be produced by
printing processes to a critical extent determines the respective
layer properties, the choice of this material has a significant
influence on every component containing this component layer.
Important parameters for printed semiconductor layers are their
respective charge carrier mobilities and the processabilities and
processing temperatures of the printable precursors used in the
production of the layers. The materials should have a good charge
carrier mobility and be able to be produced from solution and at
temperatures significantly below 500.degree. C. in order to be
suitable for a large number of applications and substrates. It
would likewise be desirable for the semiconducting layers produced
to be optically transparent for many new types of applications.
[0004] Indium oxide (indium(III) oxide, In.sub.2O.sub.3) is, owing
to the large band gap in the range from 3.6 to 3.75 eV (measured on
vapour-deposited layers, H. S. Kim, P. D. Byrne, A. Facchetti, T.
J. Marks; J. Am. Chem. Soc. 2008, 130, 12580-12581), a very
promising and thus desirable conductor. Thin films of a few hundred
nanometres in thickness can additionally have a high transparency
in the visible spectrum of greater than 90% at 550 nm. In addition,
charge carrier mobilities of up to 160 cm.sup.2/Vs can be measured
in extremely highly ordered indium oxide single crystals. However,
such values have hitherto not been able to be achieved by
processing from solution (H. Nakazawa, Y. Ito, E. Matsumoto, K.
Adachi, N. Aoki, Y. Ochiai; J. Appl. Phys. 2006, 100, 093706, and
A. Gupta, H. Cao, Parekh, K. K. V. Rao, A. R. Raju, U. V. Waghmare;
J. Appl. Phys. 2007, 101, 09N513).
[0005] Indium oxide is often used, especially together with tin(IV)
oxide (SnO.sub.2), as semiconducting mixed oxide ITO. Owing to the
relatively high conductivity of ITO layers combined with
transparency in the visible spectrum, it is used, inter alia, in
the field of liquid crystal displays (LCD), especially as
"transparent electrode". These usually doped metal oxide layers are
produced industrially mainly by costly vapour deposition methods in
a high vacuum. Owing to the great economic interest in ITO-coated
substrates, there are now some coating processes, especially
processes based on sol-gel techniques, for indium oxide-containing
layers.
[0006] There are in principle two possibilities for producing
indium oxide semiconductors by printing processes: 1) particle
concepts in which (nano)particles are present in a printable
dispersion and are converted after the printing operation into the
desired semiconductor layer by means of sintering processes, and 2)
precursor concepts in which at least one soluble or dispersible
intermediate is converted after printing of an appropriate
composition into an indium oxide-containing layer. The particle
concept has two important disadvantages compared to the use of
precursors: firstly, the particle dispersions have a colloidal
instability which makes it necessary to employ dispersing additives
(which are disadvantageous in respect of the later properties of
the layer), and secondly many of the particles which can be used
form only incomplete layers by means of sintering (e.g. due to
passivation layers), so that particulate structures still occur to
some extent in the layers. There is a considerable
particle-particle resistance at the particle boundaries and this
reduces the mobility of the charge carriers and increases the
general layer resistance.
[0007] There are various precursor-containing formulations for
producing indium oxide layers. Thus, it is possible to use not only
indium salts but also indium alkoxides (homoleptic compounds, i.e.
compounds comprising only indium and alkoxide radicals) as
precursors in solution for producing indium oxide-containing
layers.
[0008] For example, Marks et al. describe components in the
production of which a precursor-containing composition comprising
the salt InCl.sub.3 and the base monoethanolamine (MEA) are used as
a solution in methoxyethanol. After application of the composition
by spin coating, the corresponding indium oxide layer is produced
by thermal treatment at 400.degree. C. (H. S. Kim, P. D. Byrne, A.
Facchetti, T. J. Marks; J. Am. Chem. Soc. 2008, 130, 12580-12581
and supplemental information).
[0009] WO 2011/072887 A1 describes a process for preparing
indium(III) halide dialkoxides and their use for producing indium
oxide-containing layers. Processes for producing indium
oxide-containing layers from these indium(III) halide dialkoxides
are disclosed in WO 2011/073005 A2.
[0010] Indium(III) halide dialkoxides in solution have however
hitherto not led to indium oxide-containing layers having
sufficiently good electrical properties. Indium oxoalkoxides, for
example the compounds of the generic formulae
In.sub.6O.sub.2X.sub.6(OR).sub.6(R'CH(O)COOR'').sub.2(HOR).sub.x(HNR'''.s-
ub.2).sub.y, In.sub.7O.sub.2(OH)(OR).sub.12X.sub.4(ROH).sub.x and
M.sub.xO.sub.y(OR).sub.z[O(R'O).sub.eH].sub.aX.sub.bY.sub.c[R''OH].sub.d
disclosed in WO 2012/010427 A1, WO 2012/010464 A1 and in the as yet
unpublished German application DE 10 2012 209918, lead to better
layer properties.
[0011] Despite the improvements already known, there is a
continuing need for improvements in respect of the layer forming
properties and the properties of the layers obtained. In
particular, a suitable precursor-containing solution should [0012]
be able to be processed readily, in particular in air, [0013] be
able to be converted homogeneously into the oxide, [0014] be able
to be converted into the oxide at very low temperatures and [0015]
lead to layers having excellent electrical properties.
[0016] This complex requirement profile is met by the liquid
formulation according to the invention which can be produced by
dissolving at least one indium alkoxide compound which can be
prepared by reacting [0017] an indium trihalide InX.sub.3 where
X=F, Cl, Br, I [0018] with a secondary amine of the formula
R'.sub.2NH where R'=alkyl, [0019] in a molar ratio of from 8:1 to
20:1 to the indium trihalide [0020] in the presence of an alcohol
of the generic formula ROH where R=alkyl in at least one
solvent.
[0021] Particularly good layers can be produced using formulations
containing indium alkoxide compounds in whose preparation the
secondary amine has been used in a molar ratio of from 8:1 to 15:1,
even better in a ratio of from 8:1 to 12:1, to the indium trihalide
in the reaction.
[0022] For the purposes of the present invention, an indium
alkoxide compound is in the present case a compound which has at
least one indium atom and at least one alkoxide radical and can be
prepared by the above-described reaction of the trihalide with the
secondary amine in the presence of an alcohol. Determination of the
structure of these dissolved compounds which can be obtained by the
process of the invention is difficult. However, it is assumed that
the resulting compounds are halogen-containing indium oxoalkoxide
compounds. Solid-state structures of this type have been able to be
determined by means of X-ray structure analysis. It is assumed that
similar structures for these compounds are also present in
solution. Indium oxoalkoxides are indium clusters which are bridged
by oxo radicals and may be present in ionic form and in which
valencies which are not coordinated by oxo radicals are at least
partly coordinated by alkoxide radicals. In the case of the indium
alkoxide compounds which can be obtained by the process of the
invention, it is assumed that they are usually present as salt, in
particular as halogen-containing indium oxoalkoxide anions
coordinated by cations, after the synthesis.
[0023] A particularly preferred process product is an indium
alkoxide compound of the generic formula
[In.sub.6(O)(OR).sub.12X.sub.6].sup.2-A.sub.m.sup.z (ROH).sub.x
where R=alkyl, X=F, Cl, Br, I, A=cation, z=valency of the cation,
mz=2 and x=0 to 10, which can be prepared, inter alia, using
secondary amines in a ratio of from 9:1 to 10:1. The compound can
be coordinated by alcohol molecules ROH and possibly also by other
solvents present in the reaction.
[0024] Typical cations are ammonium ions [NH.sub.yR.sub.4-y].sup.+,
preferably ammonium ions of the formula
[NH.sub.2R.sub.2].sup.+.
[0025] A very particularly preferred compound is
[In.sub.6(O)(OMe).sub.12Cl.sub.6].sup.2-[NH.sub.2R.sub.2].sup.+.sub.2
(MeOH).sub.2, which can be prepared using InCl.sub.3, Me.sub.2NH
(the latter in a ratio of from 9:1 to 10:1) and MeOH (methanol).
The structure of this as determined by X-ray structure analysis is
shown in FIG. 1.
[0026] The formulation of the invention preferably contains the
indium alkoxide compound in percentages by weight of from 0.1 to
10% by weight, preferably 0.5-5% by weight, very particularly
preferably 1-2% by weight, based on the total mass of the
formulation, in order to achieve particularly good semiconductor
layers.
[0027] The formulation of the invention further comprises at least
one solvent. In order to achieve particularly good formulations,
the at least one solvent is preferably selected from the group
consisting of primary, secondary, tertiary and aromatic alcohols
(the alcohols are particularly preferably methanol, ethanol,
butanol, tetrahydrofurfuryl alcohol and phenol), ethers (particular
preference is given to glycol ethers of the formula
ROCH.sub.2CH(R')OR'' where R=--H or --C.sub.1-C.sub.10-alkyl,
R'=--H or --CH.sub.3 and R''=--H or --C.sub.1-C.sub.10-alkyl and
cyclic ethers, in particular 2-methoxyethanol, 1-methoxy-2-propanol
and tetrahydrofuran and also anisole), esters (particular
preference is given to carboxylic esters and alkyl lactates, in
particular butyl acetate, 1-methoxy-2-propyl acetate (PGMEA), ethyl
benzoate, ethylene glycol diacetate, ethyl lactate and butyl
lactate), aromatic hydrocarbons (particular preference is given to
toluene and xylene) and nitriles (particular preference is given to
acetonitrile).
[0028] The at least one solvent is preferably selected from the
group consisting of methanol, ethanol, butanol, tetrahydrofurfuryl
alcohol, phenol, 2-methoxyethanol, 1-methoxy-2-propanol,
tetrahydrofuran, anisole, butyl acetate, 1-methoxy-2-propyl acetate
(PGMEA), ethyl benzoate, ethylene glycol diacetate, ethyl lactate,
butyl lactate, toluene, xylene and acetonitrile.
[0029] The formulation of the invention more preferably comprises
at least two, even more preferably at least three, solvents
selected from the group consisting of the abovementioned classes of
solvent.
[0030] The formulation of the invention preferably comprises at
least three solvents of which one is selected from the group
consisting of ethyl lactate, anisole, tetrahydrofurfuryl alcohol,
butyl acetate, ethylene glycol diacetate and ethyl benzoate and the
other two have a boiling point difference of at least 30.degree. C.
under SATP conditions. Particularly good results can be achieved by
means of corresponding formulations.
[0031] The best results can be achieved using a formulation
comprising the three solvents ethanol, 1-methoxy-2-propanol and
tetrahydrofurfuryl alcohol.
[0032] The formulation of the invention preferably contains the
solvent or solvents in percentages by weight of 90-99.9% by weight,
preferably 95-99.5% by weight, particularly preferably 98-99% by
weight, based on the total mass of the coating composition.
[0033] Furthermore, the composition of the invention can comprise
additives, in particular wetting additives (in particular
surfactants), defoamers, crosslinking additives, surface tension
additives and levelling additives in order to achieve advantageous
properties. If additives are present, their percentage by weight,
based on the total mass of coating composition, is less than 5% by
weight, preferably less than 2% by weight. However, the composition
of the invention preferably does not comprise any further
additives, i.e. it has been produced using exclusively the solvent
or solvents and the indium alkoxide compound(s).
[0034] To achieve particularly good properties, the formulation is
essentially water-free, i.e. it has less than 200 ppm of H.sub.2O.
Furthermore, the formulation has more preferably been produced
using essentially water-free solvents and compounds.
[0035] The present invention further provides a process for
producing the formulation of the invention, in which at least one
of the indium alkoxide compounds mentioned is mixed with at least
one solvent.
[0036] The indium alkoxide compounds used for producing the
formulation of the invention are prepared by means of a process in
which [0037] an indium trihalide InX.sub.3 where X=F, Cl, Br, I
[0038] is reacted with a secondary amine of the formula R'.sub.2NH
where R'=alkyl, [0039] in a molar ratio of from 8:1 to 20:1 to the
indium trihalide [0040] in the presence of an alcohol of the
generic formula ROH where R=alkyl.
[0041] Indium trihalides of the formula InX.sub.3 are known to
those skilled in the art and are commercially available.
[0042] Secondary amines of the formula R'.sub.2NH where R'=alkyl
are likewise prior art. The alkyl radical R' is preferably a
linear, branched or cyclic C.sub.1- to C.sub.10-alkyl radical of
the formula C.sub.nH.sub.2n+1 where n=1 to 10. Two radicals R' of a
secondary amine or two different secondary amines can also together
form an alkyl radical C.sub.nH.sub.2n. Compounds which can
accordingly be used are, for example, dimethylamine, diethylamine,
dipropylamine, pyrrolidine, piperidine and pyrrole. Preferred
radicals R' are the radicals methyl, ethyl, n-propyl and i-propyl.
Very particular preference is given to the radical R' being methyl,
since this leads to particularly good yields and particularly
stable compounds.
[0043] As alcohol ROH preference is given to using alcohols having
linear, branched, or cyclic C.sub.1 to C.sub.10-alkyl radicals of
the formula C.sub.nH.sub.2n+1 where n=1 to 10. Here too, preferred
radicals R are methyl, ethyl, n-propyl and i-propyl. The radicals R
are very preferably methyl.
[0044] The indium trihalide is preferably used in proportions of
from 0.1 to 50% by weight, particularly preferably from 1 to 25% by
weight, very particularly preferably from 2 to 10% by weight based
on the total mass of all components, in the process.
[0045] The indium trihalide can be dissolved, i.e. dissociated or
complexed on the molecular level by solvent molecules/alcohol
molecules, or dispersed in the liquid phase.
[0046] The alcohol ROH is preferably used in proportions of from 50
to 99.9% by weight, particularly preferably 75 to 99% by weight,
very particularly preferably from 80 to 96% by weight based on the
total mass of all components, in the process.
[0047] The reaction mixture of the process can further comprise at
least one liquid solvent or dispersion medium which is inert in
respect of the reaction, i.e. a solvent/dispersion medium or a
mixture of different solvents/dispersion media which does not react
with the indium trihalides under the reaction conditions.
Preference is given to using aprotic solvents, in particular
solvents selected from the group consisting of aprotic nonpolar
solvents, i.e. alkanes, substituted alkanes, alkenes, alkines,
aromatics without or with aliphatic or aromatic substituents,
halogenated hydrocarbons and tetramethylsilane, and the group
consisting of aprotic polar solvents, i.e. ethers, aromatic ethers,
substituted ethers, esters or acid anhydrides, ketones, tertiary
amines, nitromethane, DMF (dimethylformamide), DMSO (dimethyl
sulphoxide) and propylene carbonate.
[0048] If such a liquid solvent or dispersion medium which is inert
in respect of the reaction is present in the reaction mixture, its
proportion is preferably from 1 to 50% by weight, particularly
preferably from 1 to 25% by weight, very particularly preferably
from 1 to 10% by weight based on the total mass of all
components.
[0049] The secondary amine is preferably used in a molar ratio of
from 8:1 to 15:1, even better in a ratio of from 8:1 to 12:1, to
the indium trihalide in the reaction, because indium alkoxide
compounds which are particularly suitable for layer production can
then be prepared in a particularly high yield.
[0050] The process of the invention is preferably carried out by
initially charging the indium trihalide in an alcohol ROH. The
secondary amine is added in gaseous form, liquid form or as a
solution in solvents (comprising, in particular, ROH as
solvent).
[0051] The addition is likewise preferably carried out under SATP
conditions (25.degree. C. and 1.013 bar).
[0052] Since the reaction can be controlled particularly readily in
this way and leads to particularly good indium alkoxide compounds,
the dialkylamine is preferably added at a rate of from 0.5 to 5 mol
per hour and mol of indium halide, preferably from 1.15 to 2.60 mol
per hour and mol of indium halide.
[0053] The reaction mixture is more preferably heated after
addition of all components in the process. The reaction mixture is
preferably heated over a period of from 1 to 10 hours to a
temperature in the range from 40 to 70.degree. C. The reaction
mixture is more preferably heated over a time of from 1 to 5 hours
to a temperature in the range from 45 to 60.degree. C. The reaction
mixture is then cooled.
[0054] After the reaction is complete, the product or product
mixture, which usually precipitates, is preferably separated from
the other constituents of the reaction composition. This is
preferably effected by filtration. Furthermore, the separated
product mixture is preferably dried and washed by means of suitable
solvents.
[0055] Particularly good indium alkoxide compounds which can be
used for producing the formulations of the invention result when
the product obtained or the product mixture obtained is
recrystallized after separation and possibly drying and/or washing.
The recrystallization is preferably carried out in the alcohol ROH
which was also used in the synthesis of the compound. The
recrystallization is preferably carried out by dissolving the
isolated product or product mixture in boiling alcohol and
subsequently crystallizing it out at temperatures of from -30 to
0.degree. C. The supernatant solvent is discarded and the
crystalline product can be employed for further use.
[0056] The formulations of the invention are particularly
advantageously suitable for producing indium oxide-containing
coatings having improved electrical properties, in particular via
wet-chemical processes. This improvement is surprising since
substances which have a very low tendency to crystallize are
generally sought as precursors of metal oxides. However, the
compounds of the invention are often cluster compounds which thus
already have a microcrystallite structure. The desired metal oxide
layer should tend to have an amorphous rather than crystalline
character in order to possess particularly good electrical
properties. Contrary to expectations, layers which are particularly
homogeneous can be produced using the compound according to the
invention.
[0057] In this case, the term indium oxide-containing coatings
refers both to indium oxide layers and to layers which consist
essentially of indium oxide and further metals and/or metal oxides.
For the purposes of the present invention an indium oxide layer is
a metal-containing layer which can be produced from the indium
alkoxides mentioned, and comprises essentially indium atoms or
ions, with the indium atoms or ions being present in essentially
oxidic form. The indium oxide layer can optionally also comprise
proportions of halogen or alkoxide from incomplete conversion
and/or nitrogen, hydrogen and/or carbon. An analogous situation
also applies to layers which consist essentially of indium oxide
and further metals and/or metal oxides, with the proviso that this
further comprises the further metals and/or metal oxides.
[0058] Furthermore, the formulations of the invention have the
surprising advantage that they can be used particularly readily for
producing conductive or semiconducting indium oxide-containing
layers for electronic components, in particular in the production
of (thin film) transistors, diodes or solar cells.
[0059] The present invention further provides a process for
producing indium oxide-containing layers, in which a formulation
according to the invention is applied to an (optionally pre-coated
or pre-treated) substrate, optionally dried and converted by means
of heat and/or electromagnetic radiation.
[0060] The substrate used in these processes according to the
invention is preferably a substrate selected from among substrates
consisting of glass, silicon, silicon dioxide, a metal oxide or
transition metal oxide or a polymeric material, in particular PE,
PEN, PI or PET.
[0061] After coating and before conversion, the coated substrate
can also be dried. Appropriate measures and conditions for this are
known to those skilled in the art. However, the coated substrate
does not necessarily have to be dried before conversion.
[0062] The compositions of the invention are particularly well
suited in coating processes selected from among printing processes
(in particular flexo/gravure printing, inkjet printing, (reverse)
offset printing, digital offset printing and screen printing),
spraying processes ("spray coating"), rotational coating processes
("spin coating"), dipping processes ("dipcoating") and other
liquid-phase coating processes such as slot die coating processes,
slit coating processes, curtain coating processes and
doctor-blading processes.
[0063] The conversion of the structure or layer produced into
indium oxide or an indium oxide-containing layer or structure can
be carried out by a thermal route and/or by means of UV, IR or VIS
radiation.
[0064] However, particularly good results can be achieved when
temperatures of from 20.degree. C. to 550.degree. C., preferably
from 100 to 400.degree. C., particularly preferably from 150 to
350.degree. C. are used for conversion.
[0065] Furthermore, the applied formulation can, as an alternative
or in addition, be converted using electromagnetic radiation, in
particular UV radiation. Preference is given to conversion using
electromagnetic radiation having a wavelength in the range from 160
to 300 nm. Conversion can preferably be effected by means of UVO
radiation having significant radiation components in the ranges
from 250 to 258 and from 180 to 190 nm, as can be generated, for
example, by means of particular mercury vapour lamps. Conversion
using radiation from an excimer lamp or an excimer laser, in
particular using radiation having a wavelength in the range from
160 to 190 nm, is also possible.
[0066] Particularly good layers result when the applied formulation
is converted by means of heat (in particular a temperature of from
100 to 400.degree. C., particularly preferably from 150 to
350.degree. C.) and by means of electromagnetic radiation (in
particular electromagnetic radiation having a wavelength in the
range from 160 to 300 nm).
[0067] Conversion times ranging from a few seconds to a number of
hours are typically used. Conversion times are typically from 1 s
to 24 h, preferably from 10 s to 2 h, more preferably from 1 minute
to 40 minutes, particularly preferably from 1 minute to 20
minutes.
[0068] Conversion can also be aided by the layer obtained after the
coating step being brought into contact with water and/or hydrogen
peroxide before the thermal treatment, so that this layer is
firstly converted into a metal hydroxide in an intermediate step
before the thermal conversion is carried out.
[0069] Furthermore, conversion of the applied coating composition
can be carried out at normal atmospheric water content.
[0070] The quality of the layer produced by the process of the
invention can also be improved further by means of a combined
thermal and gas treatment (using H.sub.2 or O.sub.2), plasma
treatment (Ar, N.sub.2, O.sub.2 or H.sub.2 plasma), microwave
treatment, laser treatment (using wavelengths in the UV, VIS or IR
range), UV light, infrared radiation or an ozone treatment after
the conversion step.
[0071] The following examples illustrate the subject matter of the
present invention without having a limiting effect.
EXAMPLE ACCORDING TO THE INVENTION
Synthesis
[0072] In a 30 l reactor which has been freed of residual moisture,
1.30 kg of indium(III) chloride (InCl.sub.3, 5.9 mol) are suspended
under a protective gas atmosphere in 17.38 kg of dried methanol by
stirring. Dimethylamine (2.57 kg, 57 mol) is metered in via a mass
flow controller (0.86 kg/h, about 4 h) at room temperature, with a
slightly exothermic reaction being able to be observed. The
reaction mixture is then heated at 50.degree. C. for 2 hours,
cooled to room temperature and filtered. The filter residue is
washed with 4.times.500 ml of dried methanol and dried under
reduced pressure (0.1 mbar) for 8 hours. The material is dissolved
in boiling methanol and crystallized out at -20.degree. C.
Production of a Formulation
[0073] The material obtained is dissolved in a concentration of 50
mg/ml in 1-methoxy-2-propanol. The concentrate obtained is
formulated as follows: 1 part of concentrate to 2 parts of
1-methoxy-2-propanol to one part of ethanol. 3% by weight of
tetrahydrofurfuryl alcohol (THFA) are additionally added to this
formulation. All solvents used are water-free (<200 ppm
H.sub.2O) and mixing is carried out under inert conditions
(likewise water-free). The formulation obtained is finally filtered
through a 200 nm PTFE filter.
Coating
[0074] A doped silicon substrate having an edge length of about 15
mm and an about 200 nm thick silicon oxide coating and finger
structures composed of ITO/gold was wetted with 100 .mu.l of the
abovementioned formulation. Spin coating at 2000 rpm (30 seconds)
is then carried out. The coated substrate is irradiated immediately
after this coating operation with UV radiation in the wavelength
range of 150-300 nm coming from a mercury vapour lamp for 10
minutes. The substrate is subsequently heated at a temperature of
350.degree. C. on a hotplate for one hour. After conversion, a
value for the field effect mobility (in the linear range) pFET=14
cm.sup.2/Vs at 2 VDS can be determined in a glove box.
Comparative Example
Synthesis
[0075] In a 500 ml round bottom flask which has been freed of
residual moisture, 5.0 g of indium(III) chloride (InCl.sub.3, 22.5
mmol) are dissolved under a protective gas atmosphere in 250 ml of
dried methanol by stirring, leaving a residue of InCl.sub.3 of
<10% by weight (based on the amount weighed in). The metered
addition of the base dimethylamine (5.0 g corresponding to 111
mmol) is ensured by means of a massflow controller and the base is
added in the stoichiometric amount based on InCl.sub.3 at room
temperature over a period of five hours, with a slightly exothermic
reaction being observed at the beginning. The solution is
subsequently completely evaporated, the solid which remains is
taken up into 250 ml of dried methanol, the mixture is filtered
under protective gas (N.sub.2), the solid is washed a number of
times (10 operations) with dried methanol and dried at room
temperature under reduced pressure (<10 mbar) for 12 hours. The
product yield was >80 mol % of indium(III)
chlorodimethoxide.
Production of a Formulation
[0076] The material obtained is dissolved in a concentration of 50
mg/ml in 1-methoxy-2-propanol. The concentrate obtained is
formulated as follows: 1 part of concentrate to 2 parts of
1-methoxy-2-propanol to one part of ethanol. 3% by weight of
tetrahydrofurfuryl alcohol (THFA) are additionally added to this
formulation. All solvents used are water-free (<200 ppm
H.sub.2O) and mixing is carried out under inert conditions
(likewise water-free). The formulation obtained is finally filtered
through a 200 nm PTFE filter.
Coating
[0077] A doped silicon substrate having an edge length of about 15
mm and an about 200 nm thick silicon oxide coating and finger
structures composed of ITO/gold was wetted with 100 .mu.l of the
abovementioned formulation. Spin coating at 2000 rpm (30 seconds)
is then carried out. The coated substrate is irradiated immediately
after this coating operation with UV radiation in the wavelength
range of 150-300 nm coming from a mercury vapour lamp for 10
minutes. The substrate is subsequently heated at a temperature of
350.degree. C. on a hotplate for one hour. After conversion, a
value for the field effect mobility (in the linear range) pFET=8
cm.sup.2/Vs at 2 VDS can be determined in a glove box.
* * * * *